The present invention relates to a semiconductor device and a method for fabricating the same, more specifically a semiconductor device including copper interconnections formed by damascene process and a method for fabricating the semiconductor device.
Recently, as an interconnection material of semiconductor devices, copper, which has low resistivity and high electromigration resistance, is noted. Conventionally, interconnections of the semiconductor devices have been formed by depositing interconnection materials and then patterning by photolithography and dry etching. However, it is difficult to dry etch copper, which generates no volatile products. Then, in forming copper interconnections, the so-called damascene process, in which trenches and/or holes are patterned in insulating films, and then interconnection materials are buried in the trenches and holes, is used.
As a method for burying copper in trench patterns and hole patterns, CVD method, sputtering and reflow method, electrolytic plating method, etc. are considered prospective. Among them, electrolytic plating method, which has low costs and high through-puts and has good characteristics of filling the trenches and holes, is recently dominant.
As the electrolytic plating method, because of the recent higher integration of LSIs, a new burying method using a growth mechanism called bottom up growth is proposed (refer to Reference 1 (M. Georgiadou, et al., “Simulation of Shaped Evolution during Electrodeposition of Copper in the Presence of Additive”, J. Electrochem. Soc., Vol. 148, pp. C54-C58, 2001) and Reference 2 (S. Soukane, et al., “Feature Superfilling in Copper Electrochemical Deposition”, J. Electrochem. Soc., Vol. 149, pp. C74-C81, 2002)). The bottom up growth has a characteristic that the film grows preferentially on the bottom surfaces of trenches and holes, although in the conventional conformal growth, the film uniformly grows at the side walls and the bottom surfaces of the trenches and holes. Accordingly, the bottom up growth has lower probability of voids and seams remaining in trenches and holes than the conformal growth, and can fill the trenches and holes of higher aspect ratios.